From the steadily converging communications and information technologies, networks are known, such as for example the “local area network” LAN, with a multitude of stations designed for data transmission, in which the transmission of data is effected by conduction, i.e. over wires which connect the stations, while for a local network constructed in accordance with the IEEE 820.11 standard (wireless local area network, WLAN) the transmission is realized by wireless means, i.e. over a radio link, with a hybrid network of stations which are linked in via wires or radio links also being permissible in the case of a WLAN.
Stations that are connected to decentralized and non-deterministic networks of this type mostly have applications implemented on them, or in some cases permanently installed in them, which cover various services and which—depending on the nature of the station—can differ from one station to another. Thus, the convergence of networks in the information and communication technologies has led to the development of networks and services from the transmission of “non-time-critical” data, such as arises with a file transfer or the transmission of e-mails, through to networks with “time-critical” data, such as for example the transmission of streaming media, speech data (“Voice over IP, VOIP) and video conferences. One reason for these latter services are time-critical is that delays and/or loss of data is immediately detected, i.e. heard or seen, by a user, and for this reason, the associated data should be transmitted as nearly as possible in real-time.
Accordingly, a so-called quality of service has been introduced in the IEEE802.11 standard. The term quality of service (QoS) is to be understood as covering all methods which influence the data flows in LANs and WANs in such a way that the service is prioritized or arrives at the receiver with a specified quality. A prioritization approach provides for a higher priority being assigned to time-critical services, such as video-conferencing, than to non-time-critical ones, whereby data packets with a higher priority are preferentially transmitted.
A disadvantage in networks of this type is that each of the stations, at which data is ready to be transmitted, has the same right to occupy the transmission medium if the data to be sent has the same priority. As the number of transmitting stations increases, the capacity of the medium available for each station decreases steadily until it is no longer possible to adhere to quality of service parameters such as the data transmission rate and delay. The ultimate result of this, especially in connection with the provision of time-critical services such as voice or video stream transmission, is that none of these services can be handled to the satisfaction of the service user.